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Biomedical subjects

R Larsson

Publications and source records attributed to R Larsson.

At least 145 records · Page 8Linked to original sources
PubMed1992

Laboratory determination of chemotherapeutic drug resistance in tumor cells from patients with leukemia, using a fluorometric microculture cytotoxicity assay (FMCA).

An automated fluorometric microculture cytotoxicity assay (FMCA) based on the measurement of fluorescence generated from cellular hydrolysis of fluorescein diacetate (FDA) to fluorescein was employed for chemotherapeutic-drug-sensitivity testing of tumor-cell suspensions from patients with leukemia. Fluorescence was linearly related to cell number, and reproducible measurements of drug sensitivity could be performed using fresh or cryopreserved leukemia cells. A marked heterogeneity with respect to chemotherapeutic drug sensitivity was observed for a panel of cytotoxic drugs tested in 43 samples from 35 patients with treated or untreated acute and chronic leukemia. For samples obtained from patients with chronic lymphocytic and acute myelocytic leukemia, sensitivity profiles for standard drugs corresponded to known clinical activity and the assay detected primary and acquired drug resistance. Individual in vitro/in vivo correlations indicated high specificity with respect to the identification of drug resistance. The results suggest that the FMCA may be a simple and rapid method for in vivo-representative determinations of chemotherapeutic drug resistance in tumor cells obtained from patients with leukemia.

Antineoplastic Agents↗
PubMed1992

Protection of guinea pigs against soman poisoning with ferrocene carbamate.

The protective effect of ferrocene carbamate pretreatment against soman poisoning was studied in guinea pigs. At doses corresponding to 1/20 x and 1/10 x LD50 of this carbamate a 20% and 45% decrease of the acetylcholinesterase in blood and brain, respectively, was obtained. In combination with additional pretreatment, diazepam, and therapy, HI-6 and atropine, the protective ratios (LD50 of soman in treated animals/LD50 of soman in untreated animals) were around 20 and 40, respectively. Animals pretreated with the high dose of the ferrocene carbamate that survived 10 x and 15 x LD50s of soman showed no remaining signs of poisoning after 24 h. Thus, the ferrocene carbamate afforded a better protection against soman than physostigmine. The explanation for this could be due to the properties of the ferrocene carbamate, not correlated to its cholinesterase inhibiting activity. This hypothesis is discussed.

Animals↗
PubMed1992

In vitro analysis of drug resistance in tumor cells from patients with acute myelocytic leukemia.

A 72 hours fluorometric microculture cytotoxicity assay (FMCA) was used for the study of chemotherapeutic drug resistance in tumor cell suspensions from patients with acute myelocytic leukemia (AML). A marked heterogeneity with respect to sensitivity was observed for a panel of cytotoxic drugs tested in 76 samples from 60 patients with treated or untreated AML. Primary resistance to vincristine (Vcr) and prednisolone in untreated AML was observed as well as 'acquired' resistance to several other antileukemic drugs. Cross resistance patterns for AML active drugs revealed significant positive relationships between anthracyclines, VP16 and amsacrine (Amsa), whereas mitoxantrone (Mitox) was more weakly correlated. Sensitivity to cytosine arabinoside was unrelated to the anthracyclines, VP16, Amsa and Mitox but showed a significant relationship to 6-thioguanine. Several resistance modifying agents, including the novel non-immunosuppressive cyclosporin A analogue PSC 833, were able to potentiate the effects of doxorubicin and Vcr at concentrations achievable in the clinic. However, the pattern of activity was heterogenous and the frequency of responsive samples was higher in relapse compared to de novo cases. Individual in vitro/in vivo correlations based on quartile distributions of all accumulated drug sensitivity data from AML patients indicated a high specificity with respect to the identification of drug resistance. The results suggest that the FMCA may provide clinically valuable information on chemotherapeutic drug resistance in AML.

Antineoplastic Agents↗
PubMed1992

Long-term stability of heparin-surface-modified intraocular lenses in vivo.

In vivo long-term stability of intraocular lens surfaces, modified by immobilized heparin, was studied. Lenses were implanted in the anterior chamber of rabbits and analyzed for surface concentration of heparin after varying periods of time up to two years. A new method using adsorption of 125iodine-labeled protamine was developed for quantitative measurements of immobilized heparin. Another assay, based on a monoclonal antibody against heparin, was also included. The study showed that surface-immobilized heparin did not degrade or desorb to any measurable degree during a two-year follow-up.

Animals↗
PubMed1992

SDZ PSC-833--a novel potent in vitro chemosensitizer in multiple myeloma.

Multiple myeloma cell lines and patient tumor samples with and without the expression of the classical multidrug resistance (MDR) phenotype were investigated in vitro for drug induced cytotoxicity and modulation of drug resistance. Overall there was a good correlation in the cell lines between MDR expression, as measured by immunocytochemistry with monoclonal antibodies against P-glycoprotein 170 (Pgp), and in vitro resistance to doxorubicin (dox) and vincristin (vcr). Drug resistance in the cell line RPMI 8226 dox 40, expressing a high level of Pgp, was almost completely reversed by the novel non-immunosuppressive cyclosporin A (CsA) analog SDZ PSC-833 (PSC), while the chemosensitizers verapamil, CsA and quinine, in clinically achievable concentrations, were much less effective. In cell lines with low Pgp expression, PSC and the other chemosensitizers seem equally effective. The patient tumor samples were selected to represent different combinations of Pgp expression, drug resistance and effects of chemosensitizers. PSC and CsA appeared equally potent and resistance modulation was detected not only in Pgp positive, but also in Pgp negative tumor samples. Furthermore, in one case of a Pgp expression myeloma, chemosensitizers were without effect. These findings indicate the need to incorporate in vitro chemosensitivity assays with Pgp determination when the effects of MDR modulating chemosensitizers are to be studied in the clinic.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Fluoride interactions with stimulus-secretion coupling of normal and pathological parathyroid cells.

Effects of the GTP binding protein (G-protein) activator NaF on parathyroid hormone (PTH) release, cytoplasmic Ca2+ concentration ([Ca2+]i) and cAMP content of bovine as well as normal and pathological human parathyroid cells were studied using precautions to avoid CaF2 precipitation. In 0.5 mM external Ca2+, NaF inhibited PTH release and lowered the cAMP content by 50-70% of the effects attained with 3.0 mM Ca2+. The NaF-induced increase of [Ca2+]i was considerably smaller than that obtained with rise of external Ca2+. It seems likely that NaF activates the inhibitory G1-protein involved in the regulation of cAMP generation. However, it is unclear whether the sluggish rise of [Ca2+]i induced by NaF is due to a direct effect of a G-protein on Ca2+ entry, or somehow related to the G-protein mediated formation of inositol 1,4,5-trisphosphate, which is part of the signal transduction pathway normally initiated by Ca2+ binding to its receptor on the parathyroid cell surface. Inhibition of PTH release by NaF probably results from the combined effects on [Ca2+]i and cAMP content. In hyperparathyroidism (HPT) the actions of NaF were not markedly affected despite severe impairments of Ca(2+)-inhibited PTH release and Ca2+ triggered increase of [Ca2+]i. Consistent with observations of down regulation of the parathyroid Ca2+ receptor in HPT, the present results indicate that the disease perturbs signal transduction at a level proximal to the site of action for NaF.

Animals↗
PubMed1992

Regulation of parathyroid hormone release in normal and pathological parathyroid cells exposed to modulators of protein kinase C.

Effects of the protein kinase C activating phorbol ester 12-O-tetradecanoyl phorbol 13-acetate and the inhibitor 1-(5-isoquinolinyl-sulfonyl)-2-methylpiperazine (H-7) on parathyroid hormone (PTH) release were studied in normal bovine and pathological human parathyroid cells. An increase of extracellular Ca2+ from 0.5 to 3.0 mmol/l inhibited PTH release by 60% in the bovine cells with half maximal effect (ED50) at 1.31 mmol/l. This inhibition reached less than 50% in the cells from patients with primary and uremic hyperparathyroidism, and the ED50 values were 1.49 and 1.42 mmol/l, respectively. The phorbol ester (0.1 mumol/l) made secretion insensitive to changes of extracellular Ca2+, an action counteracted by H-7 (50 mumol/l) in the bovine cells, whereas H-7 alone had no effects. The phorbol ester and H-7 had opposite actions on regulation of PTH release also from cells from patients with hyperparathyroidism. However, in pathological cells H-7 alone improved Ca2+ inhibition of secretion by stimulating release in low Ca2+ concentrations and decreasing the ED50 values. The magnitude of changes in ED50 values by H-7 increased with the severity of the secretory disturbance of the pathological cells. The results indicate that increased protein kinase C activity may be a factor of importance in the pathophysiology of hyperparathyroidism.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1992

Effects of hip arthroplasty and peroperative dicloxacillin prophylaxis on renal function.

In a prospective pilot study 70 patients (age greater than 65 years) who underwent hip arthroplasty were treated with dicloxacillin, a total of 6 g given pre-, per- and postoperatively as antibiotic prophylaxis. Creatinine in serum and beta 2-microglobulin in serum and urine were determined as estimates of renal function. Values were obtained preoperatively and on days 2, 4 and 10 after operation. A slight but significant increase of serum creatinine was seen on day 2 with a gradual decrease almost down to the preoperative baseline value on day 10. Serum beta 2-microglobulin increased more gradually; the increase was significant on day 10. Raised levels of beta 2-microglobulin in urine were most pronounced: a 20-fold increase on day 2, then a slow decrease, still significant increase on day 10. This may indicate a reversible damage of proximal tubules with blocked tubular reabsorption of beta 2-microglobulin. The slightly increased levels of serum creatinine and beta 2-microglobulin would also indicate a minor reversible decrease in glomerular filtration rate. Whether these effects are caused by the operation trauma per se or by the dicloxacillin prophylaxis cannot be determined from this pilot study. It seems quite clear that hip arthroplasty with short term prophylaxis with dicloxacillin does not result in clinically important changes in renal function.

Aged↗
PubMed1992

Feasibility of the fluorometric microculture cytotoxicity assay (FMCA) for cytotoxic drug sensitivity testing of tumor cells from patients with acute lymphoblastic leukemia.

The automated fluorometric microculture cytotoxicity assay (FMCA) was used for chemotherapeutic drug sensitivity testing of fresh and cryopreserved tumor cells from patients with acute lymphoblastic leukemia (ALL) at diagnosis and relapse. The technique success rate was 87% for fresh and 81% for cryopreserved samples. Up to 16 different cytotoxic drugs were routinely tested, but neither asparaginase nor methotrexate produced dose-response related cell kill. FMCA data showed good correlation to the well established Disc assay and the drug sensitivity reported by the FMCA was in good agreement with known clinical activity. Samples from children and initial ALL tended to be more drug sensitive than those from adults and ALL at relapse, respectively. For 36 samples clinical outcome was correlated to the quartile position in comparison to all other samples for the most in vitro active drug actually given to the patient. For patients with samples in the first, second, third, and fourth quartiles, the probabilities of complete remission were 89, 57, 38, and 0%, respectively. Using the median value as cut-off line, the sensitivity and specificity of the assay were 87 and 62%, respectively. It is concluded that the FMCA with a minimum of effort and with high success rate report clinically relevant drug sensitivity profiles for ALL.

Antineoplastic Agents↗
PubMed1991

ATP is required for in vitro assembly of MHC class I antigens but not for transfer of peptides across the ER membrane.

We have translated the HLA-B27 heavy chain in vitro and studied its assembly with beta 2-microglobulin and peptide in microsomes from human cells. The assembly process requires ATP. However, the translocation of peptide across the endoplasmic reticulum (ER) membrane does not require ATP, and binding of biotinylated peptide to BiP, an ER luminal protein, occurs after ATP depletion. Proteinase K treatment of the microsomes does not block peptide translocation. Thus, ATP is required in the lumen of the ER for efficient assembly to occur. Microsomes prepared from Raji and T1 cells show similar levels of assembly, whereas assembly in T2 microsomes is 10-fold lower. This difference remains after peptide stimulation of assembly. The inefficient assembly in T2 microsomes is not due to impaired peptide translocation across the ER membrane, as no difference was found compared with microsomes from T1 cells. Instead, the defect seems to reside in the lumen of the ER.

Adenosine Triphosphate↗
PubMed1991

Differential in vitro sensitivity of human tumor and normal cells to chemotherapeutic agents and resistance modulators.

The intrinsically Vincristine(Vcr)-resistant human kidney adenocarcinoma cell line ACHN, the human acute lymphoblastic leukemia cell line L0, its more-than-100-fold Vcr-resistant subline LI00, normal human fibroblasts and lymphocytes, also tumor cells from patients with chronic lymphocytic leukemia (CLL), acute myeloblastic leukemia (AML) and solid tumors, were compared for sensitivity to cytotoxic drugs and resistance modulators (RMs). The LI00 cells showed pronounced sensitivity to the RMs verapamil (Ver), cyclosporin A (CsA) and buthionine sulfoximine (BSO) alone as well as to cisplatinum, whereas the L0 and ACHN cells, also slowly growing fibroblasts and non-proliferating lymphocytes, were considerably less sensitive. Compared with AML cells and lymphocytes, CLL cells were more sensitive to Ver and CsA alone. The cytotoxicity of Vcr was significantly increased in the Vcr-resistant ACHN and LI00, but also in sensitive L0 cells by Ver and CsA, with smaller effects on Dox and Vp-16 toxicity. Fibroblasts and lymphocytes were generally resistant to the cytotoxic agents and RM addition had only minor effects. CLL cells were more sensitive to Dox and Vcr as compared with normal lymphocytes, with potentiation of the Vcr effect by Ver and CsA. The Vcr effect in non-proliferating Vcr-resistant cells from a malignant schwannoma was potentiated by Ver and CsA, which had no effect in cells from a kidney adenocarcinoma. We conclude that cytotoxicity of RMs alone is not dependent on the proliferation rate of tumor cells and that potentiation of cytotoxic drugs by RMs may be selective for tumor cells irrespective of their initial level and mode of drug resistance.

Adenocarcinoma↗
PubMed1991

Pharmacokinetics of felodipine in chronic hemodialysis patients.

Five chronic hemodialysis patients (1 woman and 4 men, aged, 46-68 yr) were given an oral dose of 10 mg felodipine followed by 0.057 mg [3H] felodipine IV. After 5 hours, a hemodialysis treatment lasting 4 hours was performed. Blood and dialysate flows were 200 mL/min and 500 mL/min, respectively. Capillary dialyzers with 1.3 m2 cellulose acetate membrane were used. The pharmacokinetic characteristics and reduction in diastolic BP were similar to those in hypertensive patients with normal renal function and in uremic patients who were not treated with dialysis. There was no measurable removal of felodipine by hemodialysis. Dialyzer clearance of radioactive metabolites was about 10 mL/min, and only 8.9% of the dose was eliminated by the treatment. The half-life of radioactive metabolites was 10 days (6-14 days) in three patients dialyzed thrice weekly. Since the metabolites are biologically inactive, no adjustment of dose is required in hemodialysis patients.

Administration, Oral↗
PubMed1991

Doxorubicin selected multidrug-resistant small cell lung cancer cell lines characterised by elevated cytoplasmic Ca2+ and resistance modulation by verapamil in absence of P-glycoprotein overexpression.

Sublines from the small cell lung cancer (SCLC) cell lines U1285 and U1690, denoted U1285-100, U1285-250, U1690-40 and U1690-150, were adapted to grow in the continuous presence of 100, 250, 40 and 150 ng ml-1 doxorubicin (Dox), respectively. The Dox resistance was accompanied by cross-resistance to vincristine (Vcr), Vp-16 and for U1285-100 also to cisplatinum. Sublines of U1690-40 and U1285-100, cultured in absence of Dox for 4 months were only partially reversed with respect to Dox resistance. Neither the parental nor the most Dox resistance sublines had detectable levels of mdr 1 RNA but a small fraction of cells in all cell lines stained weakly positive for P-glycoprotein (P-gp). Verapamil (Ver) at 5 microM reversed the Dox resistance completely and partly in the U1690 and U1285 sublines, respectively, but did not increase the cellular accumulation of Dox. The cytoplasmic free Ca2+ concentration (Ca2+i) was close to 100 nM in both parental cell lines but elevated in the U1285-100 and U1690-40 sublines by 21 and 44%, respectively, and in U1285-250 and U1690-150 by 51 and 91%, respectively. The partly reverted sublines still showed significant but smaller elevations in Ca2+i of 10-30%. Ver was without acute or long term effects of Ca2+i in the U1285-100 and U1690-40 sublines. Selection for Dox resistance in SCLC may thus result in atypical multidrug-resistance characterised by absence of P-gp overexpression and atypical cross-resistance. Although Ver did not seem to affect Dox accumulation it may still work as a resistance modulator.(ABSTRACT TRUNCATED AT 250 WORDS)

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

Translocation of peptides through microsomal membranes is a rapid process and promotes assembly of HLA-B27 heavy chain and beta 2-microglobulin translated in vitro.

We have translated major histocompatibility complex (MHC) class I heavy chains and human beta 2-microglobulin in vitro in the presence of microsomal membranes and a peptide from the nucleoprotein of influenza A. This peptide stimulates assembly of HLA-B27 heavy chain and beta 2-microglobulin about fivefold. By modifying this peptide to contain biotin at its amino terminus, we could precipitate HLA-B27 heavy chains with immobilized streptavidin, thereby directly demonstrating class I heavy chain-peptide association under close to physiological conditions. The biotin-modified peptide stimulates assembly to the same extent as the unmodified peptide. Both peptides bind to the same site on the HLA-B27 molecule. Immediately after synthesis of the HLA-B27 heavy chain has been completed, it assembles with beta 2-microglobulin and peptide. These interactions occur in the lumen of the microsomes (endoplasmic reticulum), demonstrating that the peptide must cross the microsomal membrane in order to promote assembly. The transfer of peptide across the microsomal membrane is a rapid process, as peptide binding to heavy chain-beta 2-microglobulin complexes is observed in less than 1 min after addition of peptide. By using microsomes deficient of beta 2-microglobulin (from Daudi cells), we find a strict requirement of beta 2-microglobulin for detection of peptide interaction with the MHC class I heavy chain. Furthermore, we show that heavy chain interaction with beta 2-microglobulin is likely to precede peptide binding. Biotin-modified peptides are likely to become a valuable tool in studying MHC antigen interaction and assembly.

Amino Acid Sequence↗
PubMed1991

Accuracy of hemodialysis urea kinetic modeling. Comparison of different models.

To test the accuracy of urea kinetic modeling (UKM), the classic fixed-volume model UKMf, two variable-volume models (UKMvb and UKMvd), direct dialysis quantification (DDQ) and a partial dialysate collection method (PDC) were evaluated in 15 stable, high-hematocrit patients. Urea generation rate (G) was also determined from a 1-week collection of total dialysate and urine (OWC). The results, except distribution volumes, were highly correlated. However, Kt/V, the normalized whole-body urea clearance, was about 8% higher with UKMvb and UKMvd. Two of three simple equations for Kt/V rendered grossly deviating, but highly correlating, results. The normalized protein catabolic rate was 8% higher with UKMvd. With OWC as reference, UKMvb and UKMvd overestimated G by 19 and 15%, respectively. All results of PDC closely followed those of DDQ. This method may be an alternative for exact quantification. Before using a new UKM method it should be compared to an established reference method.

Adult↗
PubMed1991

Vasoactive intestinal polypeptide stimulates parathyroid hormone release by interaction with cyclic adenosine monophosphate production of bovine parathyroid cells.

Influence of vasoactive intestinal polypeptide, neuropeptide Y, calcitonin gene-related peptide, and substance P was investigated on dispersed parathyroid cells of adult cattle. At a physiological concentration of extracellular calcium, vasoactive intestinal polypeptide stimulated the parathyroid hormone release in a dose-dependent manner, whereas no effects were noted for the other peptides. The dependency of PTH secretion upon extracellular calcium was shifted to the right by vasoactive intestinal polypeptide at 10(-6) mol/l, with a tendency for greater effects at low (0.5 mmol/l) than high concentrations (2.0-3.0 mmol/l) of the cation. Vasoactive intestinal polypeptide significantly enhanced cAMP release of the parathyroid cells, whereas no influence was noted on cytoplasmic calcium or pH within the cells. The results suggest that vasoactive intestinal polypeptide stimulates the PTH release by interaction with cAMP production of the parathyroid cells. This effect may contribute to the development of hypercalcemia in patients with neuroendocrine tumours secreting vasoactive intestinal polypeptide.

Animals↗